چکیده انگلیسی

Abstract
This study tested effects of task requirements and knowledge on auditory distraction effects. This was done by comparing the response to a pitch change (an irrelevant, distracting tone feature) that occurred predictably in a tone sequence (every 5th tone) under different task conditions. The same regular sound sequence was presented with task conditions varying in what information the participant was given about the predictability of the pitch change, and when this information was relevant for the task to be performed. In all conditions, participants performed a tone duration judgment task. Behavioral and event-related brain potential (ERP) measures were obtained to measure distraction effects and deviance detection. Predictable deviants produced behavioral distraction effects in all conditions. However, the P3a amplitude evoked by the predictable pitch change was largest when participants were uninformed about the regular structure of the sound sequence, showing an effect of knowledge on involuntary orienting of attention. In contrast, the mismatch negativity (MMN) component was only modulated when the regularity was relevant for the task and not by stimulus predictability itself. P3a and behavioral indices of distraction were not fully concordant. Overall, our results show differential effects of knowledge and predictability on auditory distraction effects indexed by neurophysiological (P3a) and behavioral measures.

مقدمه انگلیسی

Introduction
To manage the vast amount of sensory information surrounding us, we focus on what is relevant to our current goals and filter out or ignore irrelevant input. Attention involves the interaction of both volitional (top-down knowledge) and automatic processes (stimulus-driven responses), which can influence task performance via interconnected attention networks (Corbetta and Shulman, 2002 and Posner, 1980). Attentive processes modify neural activity to facilitate task goals (Lewis et al., 2009, Sawaki et al., 2012 and Sussman et al., 2002). However, little is understood about how the stimulus-driven information is stored and monitored that might minimize or interfere with task goals. We tested the hypothesis that knowledge of the sound input, driven by the stimulus statistics, can influence the degree of distraction from the relevant task. Thus, the current study assessed the influence of sequential regularities (stimulus predictability) on behavioral performance and the degree of distraction from the main task. In our previous study, we found that the neurophysiological and behavioral indices of distraction were abated by the predictable occurrence of an irrelevant, distracting tone feature, made predictable by presentation of a visual cue prior to the distracting tone (Sussman et al., 2003). In the current study we tested whether explicit knowledge about the occurrence of a distracting event, but without explicit cueing, would similarly abate distraction effects. That is, would knowledge about the irrelevance of an upcoming event, its predictability, be enough to abate distracting effects; or was there something specific about temporal cueing (e.g., with visual or other input occurring prior to each target) that primarily influenced the distraction effect observed in previous studies (Horváth, 2013, Horváth and Bendixen, 2012, Horváth et al., 2011, Sussman et al., 2003 and Volosin and Horváth, 2014). Thus, a second issue addressed by the current paradigm was whether stimulus regularity of the sound input (predictability) would act as a form of implicit cueing, speeding reaction time to targets, and facilitating behavioral responses.
To address these questions, we merged ideas from two different paradigms, a distraction paradigm (Schröger and Wolff, 1998) and a pattern detection paradigm (Sussman et al., 2002). The modified protocol was designed so that the same physical stimulus input would be presented in three different conditions that varied only in the instructions provided to participants as to how to listen and respond to the stimuli. From the pattern detection paradigm (Sussman et al., 2002), a regularly repeating five-tone sequential pattern of stimuli was presented with two different tone frequencies (MMMMHMMMMH…), where “M” denotes a middle frequency tone and “H” denotes a higher frequency tone. Another lower frequency tone (L) occurred rarely and served to disrupt the regularly occurring MMMMH pattern (pattern violation). From the auditory distraction paradigm, randomly, half of all the tones were a shorter duration than the other half of the tones (Schröger and Wolff, 1998). The participants' task was to discriminate sound duration in all conditions, pressing one key for the shorter tones and another key for the longer tones. The change in frequency from the M to the H tone was always irrelevant to the tone duration judgment task and served as a potential distracting element of the sequence.
Reaction time (RT) and hit rate (HR) on the primary (tone duration judgment) task was used to quantify effects of knowledge on behavioral distraction: longer RT and lower HR as evidence of distraction. Event-related brain potentials (ERPs) were recorded to assess neurophysiological effects of distraction induced by conditions of knowledge and task. The two dependent ERP measures used were the mismatch negativity (MMN) and P3a components elicited by the regular H tones. The MMN component is elicited by infrequent violations to detected regularities in the sound input (Näätänen et al., 2001) regardless of the direction of attention. However, because MMN is strongly influenced by sound context (which can be implicitly or explicitly determined), and by task performance (involving explicit knowledge of the sound sequence) (Sussman, 2007 and Sussman et al., 2013), its elicitation will index when the “H” tone is detected as a frequency deviant, that is, whether or not it was detected as an element of a repeating five-tone (MMMMH) pattern (Sussman and Gumenyuk, 2005 and Sussman et al., 2002). The P3a component reflects involuntary orienting away from a primary task to attention-capturing infrequently occurring deviant events (Friedman et al., 2001). Thus, elicitation of the P3a to the pattern-ending H tone will provide an index of distraction, by indexing involuntary orienting to the task-irrelevant pitch change (Schröger and Wolff, 1998 and Sussman et al., 2003). P3a is not elicited by standard repeating regularities in a tone sequence.
Conditions were distinguished by the instruction given to participants about how to listen and respond to the patterned sound sequences. In one condition participants were uninformed about the task (Uninformed condition [UNINF]). In accordance with other studies ( Jankowiak and Berti, 2007 and Sussman et al., 2002), we expected that participants would not notice the regular occurrence of the H tone. Accordingly, we expected that the pitch changes (H tones) would elicit MMN and would reflect the involuntarily capture of attention indexed by elicitation of the P3a component. Behavioral distraction effects seen as longer RT and lower HR were likewise expected ( Jankowiak and Berti, 2007). This condition was expected to replicate the findings of an auditory distraction paradigm, with the participant having no explicit knowledge of the regularly repeating H tone, and this regularity being irrelevant to the duration judgment task.
In another condition, participants were told about the patterned structure of tone presentation, so that the regular pitch change could be fully predicted (Informed condition [INF]). Thus, knowledge about the irrelevant pitch change was provided in advance, instead of in the form of a cue occurring prior to the tone. This knowledge was in the form of information about the structure of presentation of the sound sequence. If the same type of ‘cueing’ effect (i.e., knowledge about the relevance of the pitch change given in advance) could be implemented by top-down knowledge, then it should have the same abating effect as the cueing paradigm and hence there should be no behavioral distraction effect and a smaller or abolished P3a component ( Berti, 2008, Horváth, 2014, Horváth et al., 2011, Horváth and Bendixen, 2012, Horváth et al., 2008, Sussman et al., 2003, Volosin and Horváth, 2014 and Wetzel and Schröger, 2007). Additionally, because the regularity is explicit during the task, we also expected that the MMN component could be abolished because the H tone was part of the regularity in the sequence and was not a pitch change per se ( Sussman, 2013, Sussman and Gumenyuk, 2005, Sussman et al., 1998 and Sussman et al., 2002). However, the regularity was not relevant for the primary task, which was a duration judgment task.
In another condition, the sequential regularity was central to the task in addition to the duration task, so that we could assess the effects of the regularity by task-relevance and not simply by explicit expectation. Participants were instructed to detect pattern violations along with the task of identifying the duration of the tones (Informed-Detect Pattern Violation [INF-DV]). Thus, in the INF-DV condition, the pattern was made relevant to the task. The relevancy of the pattern to the task goal predicts that MMN would not be elicited by the H tones because the H tones would be part of the regularity involved in the task. We also expected that the tones that were part of the regularity should not evoke distraction effects because they would be fully predicted as part of the task. Only the unexpected infrequent pattern violations were expected to elicit the MMN and P3a components, and reflect behavioral distraction effects. In this way, elicitation of the MMN, or its absence, would index when the pattern regularity was maintained in memory during task performance, with the absence of MMN indicating that the five-tone pattern regularity was neurophysiologically maintained in memory. Elicitation of the P3a would index effects of distraction (involuntary orienting to an unexpected sound change), and further index whether or not pattern regularity and distraction effects were coupled. If explicit cueing is required to abate distraction effects, then the implicit regularity in the sequence should not be enough to do so, and abatement of the ERP distraction effects should only be observed if the regularity was explicitly used to perform the main task.

نتیجه گیری انگلیسی

Results
3.1. Behavioral responses
Table 1 displays the HR, RT, and distraction effect for each stimulus type, in each condition.
Table 1.
Behavioral data.
Condition Stimulus type HR RT Distraction effect
Uninformed (UNINF) M .87 (7) 487 (66) (H–M) 23 (25)
H .79 (12) 510 (70) (L–M) 72 (44)
L .77 (11) 559 (97)
Informed (INF) M .89 (5) 467 (64) (H–M) 23 (27)
H .80 (12) 489 (71) (L–M) 65 (44)
L .77 (10) 531 (95)
Informed-Detect Pattern Violation (INF-DV) M .86 (8) 463 (64) (H–M) 28 (39)
H .77 (16) 492 (67)
L .78 (14)a –
Mean hit rate (HR), reaction time (RT) in milliseconds and distraction effect in milliseconds.
M = frequent regular (880 Hz) tone; H = infrequent regular (988 Hz) tone; L = rare random (748 Hz) tone.
Standard deviation in parentheses.
a
HR = correct rejection (no-go).
Table options
3.1.1. Hit rate
Participants correctly identified significantly more tone durations when responding to pitch repetitions (M tones, p = 0.87) compared to pitch changes (regular H or random L tones, p = 0.79 and 0.77, respectively). There was a main effect of stimulus type (F1.58,20.54 = 10.99, p = 0.001, ηp2 = 0.46). This included correct ‘no-go’ responses for the L tones in the INF-DV condition. There was no main effect of condition on HR (F2,26 < 1, p = .59), and no interaction between factors (F4,52 < 1, p = .85).
3.1.2. Reaction time
Testing effects between the UNINF and INF conditions for all three stimulus types, responses were fastest to the M tones overall (main effect of stimulus type, F1.47,19.14 = 29.36, p < .0001, ηp2 = 0.69). Post hoc calculations showed that RT, overall, was fastest to the regular M tone (477 ms). The RT to the fifth tone of the regular pattern (500 ms), the H tone, was significantly slower than the M tone, and significantly faster than the RT to the random L tone (545 ms). RT was slowest to the L tone. There was also a main effect of condition (F1,13 = 12.29, p = 0.004, ηp2 = 0.49), with overall significantly faster RT in the INF condition (496 ms) compared to the UNINF condition (519 ms). There was no interaction between factors (F2,26 < 1, p = .54).
To test effects of implicit (UNINF) and explicit (INF and INF-DV) knowledge of the regularity of the H tone (terminal position of the five-tone pattern), the M and H tones were compared across all three conditions. There was a main effect of condition (F1.32,17.19 = 5.78, p < .021, ηp2 = 0.31). Post hoc calculations showed that RT was significantly slower, overall, in the UNINF condition (499 ms) compared to INF (478 ms) and INF-DV (478 ms) conditions, with no difference between the informed conditions. There was a also a main effect of stimulus type (F1,13 = 13.98, p = 0.002, ηp2 = 0.52), due to a significantly faster RT overall to the regular M tone (473 ms) than the regular (pattern ending) H tone (497 ms).
3.1.3. Distraction effect
There was no effect of condition on the behavioral distraction effect for the regular, pattern-ending H tone (F2,26 < 1, p = 0.78), or the random L tone between the INF compared to the UNINF conditions (t13 < 1, p = 0.33) ( Table 2). There was a significantly larger distraction effect between the overall mean of the L tones (M = 68) and the overall mean of the H tones (M = 25) (t13 = 4.07, p = 0.001).
Table 2.
Difference waveforms (ERP to H-tone minus ERP to M-tone). Mean amplitude [in μV] (standard error of the mean in parentheses) (interval used for statistical measurement in parentheses).
Component Condition Electrode
Fz Cz Pz
MMN
(96–136 ms) UNINF − 1.97 (0.36) − 1.86 (0.31) − 1.15 (0.29)
INF − 1.39 (0.32) − 1.51 (0.31) − 1.2 (0.24)
INF-DV − 0.73 (0.34) − 0.62 (0.37) − 0.33 (0.35)
P3a
(256–316 ms) UNINF 2.99 (0.71) 3.21 (0.72) 2.14 (0.61)
INF 1.83 (0.53) 1.78 (0.60) 1.27 (0.58)
INF-DV 1.04 (0.44) 1.54 (0.50) 1.37 (0.42)
Table options
3.2. ERP results
Fig. 2 displays the mean ERPs evoked by the H and M tones. Fig. 3 displays the mean H-minus-M-tone difference waveforms and the scalp voltage maps showing the topographical distribution for the MMN and P3a components. In the MMN latency range (at the Fz electrode), a negative deflection was observed peaking approximately 116 ms, with a fronto-central scalp distribution. A polarity inversion was observed at the mastoids, which is often observed when a nose reference is used (Vaughan and Ritter, 1970). In the P3a latency range (at the Cz electrode), a positive deflection was observed, peaking approximately 286 ms, having a more central scalp distribution than the MMN. Table 2 summarizes the mean difference waveform amplitudes of the ERP components.
Event-related brain potentials (ERPs) elicited by the M (gray line) and H (black ...
Fig. 2.
Event-related brain potentials (ERPs) elicited by the M (gray line) and H (black line) tones of the five-tone pattern (MMMMH) for the Uniformed (UNINF, left column), Informed (INF, middle column), and Informed-Detect Pattern Violation (INF-DV, right column) conditions displayed for the Fz (top row), Cz (second row), Pz (third row), and Left Mastoid (LM, bottom row) electrodes. Clear P1, N1, and P2 peaks were elicited by both M and H tones in all conditions.
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Difference waveforms (ERPs elicited by the M tone are subtracted from the ERPs ...
Fig. 3.
Difference waveforms (ERPs elicited by the M tone are subtracted from the ERPs elicited by the H tone). A. Scalp voltage topography of the difference waveforms is displayed for each condition (UNINF, INF, and INF-DV) at the peak latency of the MMN (top panel) and P3a (bottom panel) components. The black circle depicts the Fz electrode location. B. Difference waveforms are overlain separately at the Fz (top row), Cz (second row), Pz (third row), and LM (bottom row) electrodes for the UNINF (solid, black line), INF (dotted line), and INF-DV (dashed line) conditions. The MMN peak is labeled with an arrow at the Fz electrode and the P3a peak is labeled with an arrow at the Cz electrode (greatest S/N ratio, respectively).
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3.2.1. MMN component
MMNs were elicited by the H tones in the UNINF and INF conditions but not in the INF-DV condition (Fig. 3). This was statistically shown by a significant interaction between condition and stimulus type (F1.52,19.72 = 4.49, p = 0.033, ηp2 = 0.26). Post-hoc calculations showed that the mean amplitude elicited by the H tone was significantly more negative than the mean amplitude elicited by the M tone, in the UNINF and INF conditions, but with no significant difference between H and M in the INF-DV condition. Moreover, there were no significant differences among the M tones (− 1.19μVUNINF, − 1.28μVINF, − 1.24μVINFDV). Thus, the effects of condition on stimulus type were due to differences in response to the pattern-ending H tones. Post hoc calculations showed that the mean amplitude in the UNINF condition (− 3.16 μV) was significantly more negative than in the INF-DV (− 1.97 μV), but with no difference between the H-tone response in the UNINF and the INF (− 2.67 μV). There was a main effect of stimulus type (F1,13 = 30.78, p < 0.0001, ηp2 = 0.70), with the overall H tone amplitude more negative than the overall M tone amplitude. There was also a main effect of condition (F1.47,19.11 = 4.49, p = 0.035, ηp2 = 0.26). Post hoc calculations showed that the amplitude was smallest in the INF-DV condition than both other conditions. The overall mean amplitude between the UNINF and INF conditions (i.e., between the two conditions that significant MMNs were elicited) did not significantly differ. MMN was significantly elicited when the pattern regularity was not relevant to the task.
3.2.2. P3a component
P3a was elicited in all conditions (Fig. 3) as revealed by a main effect of stimulus type (F1,13 = 17.67, p = 0.001, ηp2 = 0.58) showing that the amplitude of the pattern-ending H tone was significantly more positive than the amplitude of the regular M tone. P3a amplitude was significantly larger in the UNINF condition (larger difference between the H and M tone amplitudes) than in the informed conditions (INF and INF-DV), demonstrated by a significant interaction between stimulus type and condition (F1.35,17.6 = 5.19, p = 0.027, ηp2 = 0.29). Post hoc calculations showed a significantly more positive response to the H tone than M tone in the UNINF than in the INF and INF-DV conditions. Further, the interaction showed no significant differences among the M tones. There was also a main effect of condition (F1.51,19.64 = 7.36, p = 0.007, ηp2 = 0.36). Post hoc tests showed that the amplitude was overall greater in the UNINF condition than the informed conditions, with no significant difference in amplitude between the INF and INF-DV conditions. This suggests an influence of explicit knowledge of the structural regularity on involuntary orienting indexed by P3a (significantly lower amplitude in the informed conditions).